The present invention relates to a reserve/release control method and in particular, to a reserve/release control method of a storage device permitting shared access from a plurality of devices and performing exclusive control to access from a plurality of devices and a computer system to which the method is applied.
As a method for permitting shared access from a plurality of information processing devices and realizing exclusive control of access from a plurality of information processing devices, there is known a reserve/release control method by reserve/release of the SCSI (Small Computer system Interface) command defined by the ANSI (American National Standards Institute). This is disclosed, for example, in dpANS SCSI Primary Commands—2 (SPC-2), Revision 20, 18 Jul. 2001, p 156-158.
According to this technique, when a plurality of clients share a single storage device as a target device, exclusive control is performed as follows. Firstly, a privileged client among a plurality of clients reserves the storage device and then the privileged client assigns (switches) the access permission right to another client, thereby performing exclusive control. This switching process is realized by using the third parity reservation function of the reserve command and the superseding reservation function.